1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a reel onto which recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes and the like are used as external recording media for computers and the like. “One-reel” recording tape cartridges, which rotatably accommodate a single reel onto which a recording tape is wound in a case, can reduce space requirements for accommodation during storage and can record large amounts of information, and are employed as such recording tapes.
Such a recording tape cartridge is equipped with a braking structure such that the reel does not rotate inside the case at times of non-use (see, for example, the specification of Japanese Patent Application Laid-Open (JP-A) No. 63-251983). A recording tape cartridge equipped with this braking structure is now described with reference to FIG. 11.
In a recording tape cartridge 200 shown in FIG. 11, a single reel 204 is accommodated in a case 202. The case 202 is provided with a gear aperture 206 and a rotation-limiting rib 208. The gear aperture 206 is formed at a central portion of a floor plate 202A of the case 202. The rotation-limiting rib 208 protrudes downward from a ceiling plate 202B of the case 202.
The reel 204 is provided with a reel hub 210, which is formed in the shape of a circular tube with a base, around an outer peripheral portion of which recording tape is wound. At a lower face (outer side) of a base portion 210A of the reel hub 210, a reel gear 214 is formed in an annular shape. The reel gear 214 is meshable with a driving gear 212A, which is formed at a rotation shaft 212 of a drive device.
At an upper face (inner side) of the base portion 210A, an engaging gear 216 is formed in an annular shape. A through-hole 218 is formed in an axial center portion of the base portion 210A. An annular reel plate 219 is fixed at a radial direction inner side of the reel gear 214 at the lower face of the base portion 210A. The reel plate 219 is formed of a magnetic material and includes, at an axial center portion thereof, a through-hole which substantially corresponds with the through-hole 218.
A disc-like brake member 220 is insertedly provided inside the reel hub 210. An annular brake gear 220A is provided at a lower face of the brake member 220. The brake gear 220A is meshable with the engaging gear 216. An engaging projection 222 is provided standing from an upper face of the brake member 220. The rotation-limiting rib 208 of the case 202 is inserted into the engaging projection 222, and renders the brake member 220 incapable of rotating relative to the case 202 but capable of moving in a vertical direction of the case 202. Meanwhile, an engaging projection 223 is provided protruding from an axial center portion of a lower face of the brake member 220. The engaging projection 223 enters into the through-hole 218 of the reel hub 210 and faces the gear aperture 206.
A compression coil spring 224 is disposed between the ceiling plate 202B of the case 202 and the brake member 220. The brake member 220 is continuously urged downward by urging force of the compression coil spring 224, and the brake gear 220A is meshed with the engaging gear 216.
Accordingly, at times when the recording tape cartridge 200 is not in use, the recording tape cartridge 200 is set to a rotation-locked state in which rotation of the reel 204 relative to the case 202 is blocked. Further, the reel 204 is pressed against the floor plate 202A of the case 202 by the urging force, and the reel gear 214 is exposed through the gear aperture 206.
On the other hand, when the recording tape cartridge 200 is being loaded at a drive device, in accordance with an operation in which the driving gear 212A meshes with the reel gear 214, a releasing portion 212B, which is provided protruding from an axial center portion of the rotation shaft 212, abuts against the engaging projection 223 of the brake member 220 and pushes the same.
As a result, the brake member 220 is pushed upward, against the urging force of the compression coil spring 224, and the meshing of the brake gear 220A with the engaging gear 216 is released. In a state in which the driving gear 212A and the reel gear 214 are fully meshed, the reel plate 219 of the reel 204 is attracted to an annular magnet 212C, which is provided between the driving gear 212A and the releasing portion 212B of the rotation shaft 212. Thus, the reel 204 is rendered capable of rotation within the case 202, and this meshing is maintained.
Hence, when the rotation shaft 212 rotates about the axis thereof, the reel 204 rotates integrally therewith. At such a time, because the brake member 220 is non-rotatable relative to the case 202, the engaging projection 223 and releasing portion 212B slidingly contact one another. In order to reduce rubbing resistance thereat, the engaging projection 223 of the brake member 220 is formed of a resin material, and the releasing portion 212B of the drive device is correspondingly formed with a resin material.
However, the recording tape cartridge 200 with the structure described above has the following problems. Firstly, because the engaging projection 223 and the releasing portion 212B rub against one another in accordance with rotation of the reel 204, if speeds of rotation of the reel 204 are increased and/or continuous rotation times are lengthened, one or both of the engaging projection 223 and the releasing portion 212B will become worn. In such a case, if it is the engaging projection 223 that becomes worn, it is possible to arrange for replacement of that component. However, if the releasing portion 212B of the drive device becomes worn, maintenance is troublesome and maintenance costs are high.
Secondly, because the relatively large engaging projection 223 is provided protruding from the lower face of the brake member 220, a center of gravity of the brake member 220 as a whole is high (a condition similar to a spinning top), and large vibrations may be caused by slight offsets during rotation of the reel 204. Such vibrations are a cause for the generation of abrasion dust due to continuous sliding of the rotation-limiting rib 208 against the engaging projection 222, increases in wear of the engaging projection 223 and/or the releasing portion 212B, and the like. In order to prevent this, a distal end of the engaging projection 223 has a flat surface 223A, which makes surface contact with the releasing portion 212B. However, the area of the flat surface 223A is very small, so as to reduce the aforementioned sliding resistance, and is not large enough to prevent these vibrations. Furthermore, if a protrusion length of the engaging projection 223 is reduced, it is necessary to make the releasing portion 212B of the drive device longer, and a relative stroke in the axial direction when the driving gear 212A is meshing with the reel gear 214 is greater, which leads to an increase in size of the drive device.
Thirdly, the rotation shaft 212 is structured with a metallic material, due to requirements of strength, endurance and the like, while, as mentioned above, the releasing portion 212B mounted at the rotation shaft 212 to correspond with the brake member 220 is structured with a resin material. However, because the magnet 212C is disposed around the releasing portion 212B, it is not possible to affix the releasing portion 212B from the upper side (the recording tape cartridge 200 side). Consequently, the releasing portion 212B is fixed to the rotation shaft 212 by fixing with screws from a side of driving by a motor or the like, as shown in the illustration. Thus, arrangements of a motor and the like in the drive device are limited. In other words, degrees of freedom of design of the recording tape cartridge 200 and of drive devices in which the recording tape cartridge 200 is to be loaded have been limited.
Accordingly, structures in which a release member is interposed between the brake member 220 and the rotation shaft 212 are known (see, for example, JP-A No. 11-185437 and Japanese Patent No. 3,187,022).
A structure of JP-A No. 11-185437 is equipped with a release member with a view to dust-protection. This release member is formed of a resin and is relatively rotatable with respect to both a brake member and a reel. Thus, this release member is not a solution to the problems described above.
On the other hand, a structure in the specification of Japanese Patent No. 3,187,022 is equipped with a release member as a countermeasure to the problems described above. Accordingly, parts of this structure that differ from the recording tape cartridge 200 will be described with reference to FIGS. 12 and 13.
A recording tape cartridge 250, which is shown in FIG. 12, is provided with a release member 252 formed of resin, which is disposed between the base portion 210A of the reel hub 210 and the brake member 220. As shown in FIG. 13, the release member 252 is formed in a substantially equilateral triangle shape in plan view, and is provided with leg portions 254 which are provided protruding downward from the corner portions thereof. The leg portions 254 respectively enter into insertion through-holes 256, which are formed in the base portion 210A instead of the through-hole 218, and face the gear aperture 206.
The insertion through-holes 256 penetrate through the base portion 210A at a region at which the reel gear 214 is formed. A diameter of each insertion through-hole 256 is set to be larger than a gear pitch of the reel gear 214, and teeth of the reel gear 214 are not provided in a vicinity around each insertion through-hole 256. Meanwhile, a plurality of engaging protrusions 258 is provided at the upper face of the base portion 210A, instead of the engaging gear 216. The engaging protrusions 258 are disposed at equal intervals along a predetermined circular circumference, so as not to coincide with the corner portions of the release member 252. Gear teeth 258A, which are meshable with the brake gear 220A, are formed at upper ends of the engaging protrusions 258.
A sliding protrusion portion 260 is provided protruding from an axial center portion of an upper face of the release member 252. The sliding protrusion portion 260 continuously abuts against a sliding protrusion portion 262, which is provided instead of the engaging projection 223 at the brake member 220.
With this recording tape cartridge 250, at times of non-use, the brake gear 220A of the brake member 220 is meshed with the gear teeth 258A of the reel 204 by the urging force of the compression coil spring 224. Hence, rotation of the reel 204 relative to the case 202 is blocked. In this state, the release member 252 abuts against the brake member 220 at the sliding protrusion portion 260, and the lower face of the release member 252 is pressed against the base portion 210A. Furthermore, end faces of the leg portions 254, which are disposed in the respective insertion through-holes 256, are substantially flushd with tooth peaks of the reel gear 214.
On the other hand, when the recording tape cartridge 250 is being loaded in a drive device, the reel gear 214 meshes with the driving gear 212A of the rotation shaft 212, at which the releasing portion 212B is not provided. In accordance with this meshing, the leg portions 254 are pushed by the driving gear 212A, and the release member 252 is pushed upward against the urging force of the compression coil spring 224.
Accordingly, the release member 252 is separated from the base portion 210A while the brake member 220 is being pushed upward, and the meshing of the brake gear 220A with the gear teeth 258A is released. While the meshing of the driving gear 212A with the reel gear 214 is maintained, the leg portions 254 of the release member 252 are in contact with the driving gear 212A. Thus, this structure retains the brake member 220 at the released position.
Hence, when the rotation shaft 212 rotates, the reel 204 rotates inside the case 202. At such a time, the release member 252, whose leg portions 254 are inserted in the insertion through-holes 256 of the reel 204, rotates integrally with the reel 204, and the sliding protrusion portion 260 of the release member 252 rubs against the sliding protrusion portion 262 of the brake member 220.
As descried above, in the recording tape cartridge 250, the release member 252, which abuts, at the respective leg portions 254, against the tooth peaks of the driving gear 212A of the rotation shaft 212, rotates integrally with the reel 204. Therefore, there are no locations at which the drive device rubs against the recording tape cartridge 250 in accordance with the rotation of the reel 204, and there is no risk of drive device side members becoming worn. Furthermore, because the release member 252 is interposed between the brake member 220 and the rotation shaft 212, the position of the center of gravity of the brake member 220 is lower, and vibrations of the brake member 220 during rotation of the reel 204 are suppressed.
In particular, because the release member 252 is pushed by the rotation shaft 212 at the leg portions 254 which are disposed to be distant from the axial center of the reel 204, an attitude of the release member 252 during rotation of the reel 204 is stable, and is unlikely to cause vibrations of the brake member 220.
Further, because the rotation shaft 212 pushes the release member 252 with the driving gear 212A, there is no need to provide the releasing portion 212B which is fabricated of resin, and the structure of the recording tape cartridge 250 does not apply limitations to layouts of motors and the like in drive devices. Note that the magnet 212C is not shown in FIG. 12.
However, even the conventional recording tape cartridge 250 as described above has problems, as follows.
Firstly, the leg portions 254 of the release member 252, which is fabricated of resin, are pushed by the tooth peaks of the driving gear 212A, which is fabricated of metal, for moving the brake member 220 to a rotation-enabling position and holding the brake member 220 at that position. Therefore, even though there is no sliding contact between the release member 252 and the driving gear 212A in accordance with the rotation, the leg portions 254 will be subject to wearing by usage over long periods (i.e., being repeatedly pushed).
Secondly, because the release member 252 is moved upward by the driving gear 212A which meshes with the reel gear 214, a movement stroke of the release member 252 is limited by a height of the teeth of the reel gear 214 (and the driving gear 212A), and it is difficult to ensure a generous release stroke. In particular, if the leg portions 254 are worn as mentioned above, the release member stroke is reduced and there is a risk that lock-releasing of the reel 204 may not be effected. If, in order to counter this, the leg portions 254 are made to protrude beyond the tooth peaks of the reel gear 214, there is a risk that locking of the reel 204 will be released at times of non-use.
Thirdly, the reel gear 214 is formed in a large-diameter annular form as a whole, in order to reduce driving force from the rotation shaft 212. Thus, at the base portion 210A, the reel gear 214 is disposed to be separated as far as possible from the axial center. Meanwhile, in order to guarantee braking force from the brake member 220, the engaging protrusions 258 featuring the gear teeth 258A are disposed on a circular circumference with as large a diameter as possible. Thus, the reel gear 214 and the engaging protrusions 258 are arranged in the vertical direction at substantially the same position, or the reel gear 214 that is formed at the outer face side is disposed slightly to a radial direction outer side relative to the engaging protrusions 258.
Consequently, because the engaging protrusions 258 should not interfere with the corner portions of the release member 252 (portions thereof which correspond to the region at which the reel gear 214 is formed), the engaging protrusions 258 cannot be provided with a continuous annular form. In consequence, the engaging protrusions 258 have to be provided partially and, in comparison to the engaging gear 216 that is provided in an annular form, a centering function (centripetal force) of the brake member 220 due to the meshing thereat is weak.
When the centering function of the recording tape cartridge 250 is poor, it is likely, particularly during assembly of the brake member 220, that the brake member 220 will ride up on the gear teeth 258A, and careful operation (in the case of an automatic assembly device, a high level of monitoring) is necessary. Furthermore, the reel gear 214 is similarly non-continuous in the circumferential direction, because of the insertion through-holes 256. As a result, the centering function is weakened, and torque that can be transmitted from the rotation shaft 212 is reduced.
Fourthly, because the release member 252 is disposed in the reel hub 210, a rotation-locking position of the brake member 220, which is disposed to be separated from the reel hub 210, is raised by an amount corresponding to thickness of the release member 252, and braking of the reel 204 by the brake member 220 may be inconsistent.
Furthermore, because the rotation-locking position is higher, a protrusion height of the engaging protrusions 258 from the reel hub 210 is higher than with the engaging gear 216, and the engaging protrusions 258 form thick portions at the reel hub 210. As a result, flow characteristics of resin during formation of the reel hub 210 that is formed of a usual resin are poor, which leads to a deterioration in formation characteristics.
As described above, there is still room for improvement of a release member for releasing a state in which a reel is locked by a brake member.